1. Field of the Invention
The present invention relates to a seal mechanism, a seal trench, a seal member, and a substrate processing apparatus, and in particular to a seal mechanism of a substrate processing apparatus that generates plasma in a processing chamber, of which interior is in a vacuum and inner wall is maintained at high temperature, and carries out processing on substrates using the plasma.
2. Description of the Related Art
A substrate processing apparatus that carries out plasma processing such as etching processing on semiconductor wafers (hereinafter referred to as “wafers”) as substrates is comprised of a processing chamber (hereinafter referred to as the “chamber”) that accommodates a wafer and of which interior can be evacuated. The chamber is made of aluminum, and substantially the entire inner wall of the chamber is covered with alumite. In this substrate processing apparatus, a process gas supplied into the chamber is turned into plasma, and etching processing is carried out on a wafer by the plasma. Also, the substrate processing apparatus has a seal mechanism that seals the interior of the chamber from outside (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2006-342386).
In recent years, to increase the packing density of a semiconductor device formed on a wafer, there has been developed a semiconductor device having a multilayer structure. In a process of manufacturing such a semiconductor device having a multilayer structure, etching processing is repeatedly carried out on wafers in the same chamber from the viewpoint of increasing throughput. If the etching processing is repeatedly carried out, then deposit will become attached to surfaces of an inner wall and component parts (hereinafter referred to as “the inner wall, etc. of the chamber”). To suppress the attachment of the deposit, a substrate processing apparatus has a heating mechanism that heats the inner wall, etc. of the chamber so that the temperature of the inner wall, etc. of the chamber can increase to vaporize a reaction product and a process gas that has reached the surfaces of the inner wall, etc. of the chamber so as to suppress the attachment of the deposit.
A seal mechanism which the substrate processing apparatus has is disposed, for example, between a side wall of the chamber and an upper lid of the chamber so as to seal the interior of the chamber from outside. This seal mechanism is usually comprised of a seal member formed of an O-ring, and a seal surface that is in contact with an O-ring covered with alumite. Because the inner wall, etc. of the chamber is heated by the heating mechanism as described above, the temperature of the seal mechanism as well as the inner wall, etc. of the chamber increases. In general, the heat resistance of the alumite is low, and hence the alumite of the seal surface becomes cracked when the temperature of the seal mechanism increases. When cracking occurs, it becomes difficult to seal the interior of the chamber with the O-ring and the seal surface, and as a result, the amount of air leakage into the chamber increases.
Accordingly, to cope with the problem of the increase in the amount of air leakage caused by the increase in the temperature of the seal mechanism, there has been proposed that the alumite is removed from the seal surface to expose aluminum that does not become cracked by heat, and the seal surface of the aluminum and the O-ring are brought into contact with each other. Whereby, even if the temperature increases, sealing by the O-ring and the seal surface can be maintained, and as a result, the amount of air leakage into the chamber can be prevented from increasing.
However, if the aluminum is exposed from the seal surface, the seal surface of the aluminum corrodes due to moisture attracted to the seal surface cause by air release at the time of maintenance and a solution produced by reaction of a process gas supplied into the chamber and reaction product. The corrosion of the seal surface of the aluminum will impair the shape and strength thereof, and hence the occurrence of the corrosion has to be prevented.
Moreover, in the substrate processing apparatus, electric charges are accumulated on the alumite on the inner wall, etc. of the chamber each time etching processing is carried out, but if a seal surface from which aluminum is exposed exists in the vicinity of the inner wall, etc. of the chamber, abnormal discharge (arcing) toward the seal surface caused by the accumulated electric charges will occur when the alumite on which the electric charges are accumulated break. Because the abnormal discharge may produce particles or damage the O-ring, the abnormal discharge has to be prevented.